A new half oblate consisted model is built upon the probability distribution concept from the scattering characteristics of the particles. It is suggested that η represents the shape factor, T(η) represents the shape impact factor and P(η) represents the shape probability distribution. The size distribution function P s (a) is substituted by the character distribution function P(a,η). After that, a inversion equation of the function P(η,a) and a method for the measurement are established upon the Mie scattering theory, which is supported by using arbitrary particles such as mineral particles in the experiment, and a good result is obtained.